For example, Patent Document 1 discloses a conventional automotive seat headrest supporting apparatuses of such type. As shown in FIG. 1 of Patent Document 1, a stay locking member (30) is provided in a stay holder (20) installed in a seat back portion of an automotive seat so as to be inserted and removed from an opening (24a). An opening portion (32) and hole portions (36) are formed in the stay locking member (30), and a locking rod (50) is inserted into the hole portions (36). Part of the locking rod (50) is exposed in the opening portion (32).
Stays (headrest stays) extending from the headrest of a motor vehicle are inserted into the inserting portions (24) of the stay holder (20) and penetrate through the opening portions (32) of the stay locking members (30).
The stay locking member (30) is biased in a horizontal direction by a coil spring (40), and the locking rod (50) is brought into engagement with a stopper groove in the headrest stay by the biasing force of the coil spring (40), whereby the headrest stay is fixedly positioned in place.
The parenthesized reference numerals are those described in Patent Document 1.
In the conventional headrest supporting apparatus disclosed in Patent Document 1, the locking rod (50) is designed to be inserted into the hole portions (36) formed in the stay locking member (30) from a side thereof so as to be incorporated into the stay locking member (30). However, the hole portions (36) communicate with the opening portion (32) inside the stay locking member (30). Because of this, the hole portions (36) are formed separately in both side portions of the stay locking member (30). Therefore, since a distal end portion of the locking rod (50) which is inserted into the hole portion (36) from the side is released in the opening portion (32) on its way to the other hole portion (36), there may be a risk of the distal portion of the locking rod (50) traveling in a direction which slightly deviates from the course to the other hole portion (36). As a result, the distal end portion of the locking rod (50) cannot be led to the other hole portion (36) in a smooth fashion, resulting in more complicated locking rod (50) incorporating work having to be performed than expected.
While Patent Document 1 describes that the locking rod (50) may be molded integrally with the stay locking member (30) through insert molding (refer to paragraph [0023]), such molding method deteriorates the productivity very much, leading to a problem that the production costs are increased to become expensive.
Further, in order to prevent the dislodgement of the locking rod (50) from the hole portions (36), Patent Document 1 discloses a configuration in which a groove portion (50a) is formed in the locking rod (50), while a projection (36a) is formed on the hole portions (36) of the stay locking member (30), so that the groove portion (50a) and the projections (36a) are brought into engagement with each other (refer to paragraph and FIG. 4 of Patent Document 1).
If the above-described configuration is provided, however, a large inserting force is required for the distal end portion of the locking rod (50) to ride over the projections (36a) when the locking rod (50) is inserted into the hole portions (36). Consequently, a tool such as a hammer is necessitated to perform the incorporating work of the locking rod (50), this deteriorating the workability further.
On the other hand, if the above-described dislodgement preventing construction is not provided, the locking rod (50) may be dislodged from the hole portions (36) due to vibrations or the like caused when the vehicle is running and then may be brought into abutment with an inner wall of the stay holder (20), disturbing the smooth inserting and removing operations of the stay locking member (30).    Patent Document 1: JP-H10-295484-A